Decrypting an email

Decrypting an email

Adele has received your public key, and uses it to encrypt an email which she sends back to you.

The email will look like this:

From: Adele (The friendly email-Robot) <adele@gnupp.de>
Subject: Re: my publis key
To: larrys@gpg4win.de
Date: Thu, 12 Jan 2006 09:17:28 +0100

-----BEGIN PGP MESSAGE-----
Version: GnuPG v1.4.1 (GNU/Linux)

hQEOA9FS8I3hSvdPEAP/W6W6f4MBwqTdzd9O/7FOTDHh//bQ+GUWoT0k9Y0i96UZ
QO1VhQSia6a8DZrFQj7SlJWmB1MM7RNhkmhfZsD5Bn9ICmwwOt2xJDBkCQ34gu5N
NxQ92WXZjHCaI0dSlynNziNbK8Ik26YPBYkQjLUDhHN4CRZ7q67eVEd/B9DI04wD
....
ujbjyj09L/9NvoBniWrgqVUayKr1Ls8OIZkyiex6mKypPGADJFAzvTwjubj5S6zJ
A+QvSXUB9Hj8Ft2Nt3j0B/gWn5no3Er2/15UcBn/UPSxW9or0w9seDxCuSXvpakX
bcneOm/pcJNEHcApXWXpoNOxRZ1MksM300w+79M6p2w=
=VCHb
-----END PGP MESSAGE-----

(Please note that the encryption sequence has been considerably shortened for demonstration purposes.) Using WinPT to decrypt this email.

WinPT (Windows Privacy Tray key management tool) serves as PnuPG's "front end". This program is used to encrypt and decrypt emails; it also creates and verifies digital signatures. One of WinPT's advantages is that it works with all email programs.

Most email programs (e.g. MS Outlook for Windows) also have special plug-ins which can encrypt and decrypt an email directly within the program.

==> Chapter 8 of the manual "Gpg4win for Advanced Users" provides more information on this particular funtion.

WinPT performs the en/decryption function using your computer's memory. This means that any text to be en/decrypted must be copied onto the computer's clipboard.

To do this, highlight the complete text in Adele's email and copy it onto the clipboard using the copy function or the shortcut Ctrl-C.

Starting WinPT from Windows Start Menu:

Once you open the program, the WinPT icon (a key) appears in the Windows taskbar, which is located in the lower right hand corner of the screen.

Right-click on the icon to open the menu box, and click on Clipboard -> Decrypt/Verify.

The program will then ask you for your secret passphrase and proceed to decrypt Adele's email.

A popup window window will notify you when the decryption process is complete.

The decrypted text is now located on the clipboard, much in the same way as was done during the encryption process. You can copy the text (using shortcut key Ctrl-V) into your text editor or email program.

Adele's decrypted email will look something like this⁵:

Hello Larry Smith,

here is an encrypted response to your email. 

I received your public key with the ID 57251332CD8687F6 and a
description `<larrys@gpg4win.de>'.

I have enclosed the public key of adele@gnupp.de.

Sincerely,
adele@gnupp.de

The text sequence following this message is Adele's public key.

The next section shows you how to import someone's public key and attach it to your key ring, which allows you to use this key anytime to encrypt messages to that person (in this case, Adele) or to verify a digital signature.

Summary:

You know how to decrypt an encrypted email using your private key.
You know how to send an encrypted response using the public key of the sender.

Decrypting an email